In the construction industry, paint has been used for many years to mark boundary lines on the ground for the placement of sewer lines, electrical lines and the like. Utility companies have also applied paint onto the ground to mark the location of utility lines to ensure that they will not be disturbed. Although paint is an adequate marking composition for these applications, it tends to leave a rather permanent mark on grass or concrete. Generally, a mark should be able exist for up to a month if left undisturbed in order for it to be deemed useful in these industries but should be easy to remove when the job is completed. In addition, it is difficult to see a painted surface if one is at a distance from the surface.
Various types of foams, which are three-dimensional, a characteristic which serves to increase their visibility at long distances, have been developed for the marking of surfaces. One type of foam has been developed from soaps and detergents, this being exemplified by U.S. Pat. No. 4,597,997 to Weill. This particular foam, which is a water-based foam paint adapted for discharge from an aerosol container, comprises a foam-producing emulsion of the type commonly used in shaving cream, e.g., a mixture of one or more fatty acids and a mixture of caustic potash and caustic soda. A coloring additive is introduced while other components such as emulsifiers, emollients, thickeners, preservatives, and bactericides may also be added. In regard to the propellant, a compressed liquid or gas, such as low boiling hydrocarbons, chlorofluorocarbons, and carbon dioxide, may be employed. A major drawback of soap and detergent-based foams however is their short life, making this type of foam unsuitable for situations wherein a more durable and long-lasting foam is required.
A ground marking foam which is more durable than these aforementioned soap-based foam which can be used to indicate those areas over which fertilizing chemicals have been applied is described in U.S. Pat. No. 4,050,944 to Cartwright. This composition is initially produced in the form of a concentrate which is intended to be diluted at the point of use. The concentrate comprises a surfactant functioning as a foam producing agent (about 5 to 12 wt. percent), a foam stabilizing agent (about 1 to 10 wt. percent), and water (about 70 to 90 wt. percent). Optional components include a water softening ingredient, a buffering agent for stabilizing the pH of the composition, a viscosity reducing agent, and a water coloring ingredient or dye. This composition does not include a propellant intermixed therein nor a polymer or solvent which may enhance the stability of the resulting foam.
Other types of high-expansion foams which contain a polymer are presently known. For example, U.S. Pat. No. 4,442,018 to Rand discloses a foam-forming composition which comprises a water-soluble polymer of the polyacrylic type, a foam stabilizer of dodecyl alcohol, a surfactant, a solvent and water. This concentrate is then diluted at the point of use and is then blown through a screen to produce a foam. The preferred polymer is known by the trademark CARBOPOL 941 (B. F. Goodrich) and is a water-soluble vinyl polymer. However, this composition does not contain a propellant and, as such, is not adapted for delivery from an aerosol containment means.
In comparison, a foam-producing composition that is adapted for discharge from an aerosol container is disclosed in U.S. Pat. No. 3,705,855 to Marschner. This reference is drawn toward a reversible-emulsion aerosol system which comprises two immiscible liquids in emulsified form having water in the dispersed phase and a propellant in the continuous phase. The composition comprises about 35 to about 85 wt. percent water, 10 to 50 wt. percent liquid propellant, 0.1 to about 20 wt. percent of a water-soluble surfactant, and an effective amount of a water-in-oil emulsifier. However, this reference contains no disclosure directed toward the durability or longevity of the resulting foam product.
Foam compositions are also used in the printing industry, specifically as ink carriers. Exemplar of this type of application of foam technology is U.S. Pat. No. 4,482,648 to Norman. This reference discloses foamed ink compositions for use on printing presses and methods for making these inks. The ink disclosed comprises a water-based printing ink, a foaming agent, and a pseudoplastic additive, this ink being foamed by use of a compressed gas. In producing the foam, air is discharged from a nozzle into a chamber while, simultaneously, the composition is also introduced into the chamber. The gas mixes with the composition and flows into a receiving area. The resulting mixture is removed from the receiving area via a foam refining tube and ultimately forms a foamed ink. This ink may further comprise an aqueous pigment dispersion which has about 30 to about 60 wt. percent solids. The solids are generally resins which may be either water-soluble or water-dispersible depending upon the vehicle employed. Foam stability agents may also be employed, such as higher fatty alcohols, e.g., cetyl and stearyl alcohol, and may comprise from about 0.1 to about 10 wt. percent of the composition. Suitable pseudoplastic additives include xantham gum. This reference, however, does not disclose a composition which includes, in a single aerosol package, a foam forming composition and a propellant, which upon discharge produces a stable foam product.
Thus, there exists a need for aerosol foam marking compositions which do not suffer from the disadvantages associated with prior foam marking compositions.
Accordingly, it is an object of the present invention to provide an aqueous-based aerosol foam marking composition, which includes a propellant, wherein the composition produces a foam upon discharge from a pressurized container.
A related object is to provide an aerosol foam marking composition which does not require an additional apparatus to induce foam formation after the composition is discharged from a pressurized container.
A further object is to provide an aerosol foam marking composition which, upon discharge from a pressurized container, will produce a foam that is stable for long periods of time, i.e. from a few hours up to about 90 days, if left undisturbed.
Yet another object is to provide an aerosol foam marking composition in which pigments may be added to the composition to produce a colored foam.
An additional object is to provide an aerosol foam marking composition which is stable when exposed to high temperatures during processing and storage, i.e., between about 80 and 130.degree. F.
These and other objects and advantages of the present invention will become apparent upon review of the following summary and detailed description of the invention.